Bali, Indonesia Surf Forecast 17 - 31 August 2015

16 Aug 2016 0

Ben Macartney

Chief Surf Forecaster

COASTALWATCH | Bali, Indo Forecast

Forecast Issued Tuesday, 16 August 2016

It may not be shaping up as the most amazing fortnight of the winter season so far, but late August continues to offer up consecutive days of good waves. The magnetic allure of warm water and clean, perfect waves is an ever-present feature of the winter season, so regardless of whether your planning on relaxing between the odd surf along Bali’s Bukit Peninsula or heading further afield in search of uncrowded perfection – it’s all looking pretty good from my office-chaired perspective.

The Mentawaiis have seen their fair share of excellent days through the month of August. Photo: Nick O'Brien.

The Mentawaiis have seen their fair share of excellent days through the month of August. Photo: Nick O'Brien.

Short Forecast
A consistent run of small to mid-sized SSW swell maintains fun surf across exposed breaks right through to the end of August.

Daily Summary

Wednesday 17
Easing SSW groundswell. Sets up to 3 - 4ft exposed breaks. Grading smaller elsewhere depending on exposure. WIND: Early light and variable tending ESE 10 to 15 knots.

Thursday 18
Mid period SSW groundswell. Sets around 3 – 4ft exposed breaks, easing during the afternoon. Grading smaller elsewhere depending on exposure. WIND: Early light and variable tending ESE 10 to 20 knots.

Friday 19
SSW groundswell. Sets around 2 – 3ft+ exposed breaks, grading smaller elsewhere depending on exposure. WIND: Early light and variable tending ESE 10 to 15 knots.

Saturday 20
New SSW groundswell. Sets around 4 – 5ft+ exposed breaks. Grading smaller elsewhere depending on exposure. WIND: Light and variable tending ESE 8 to 12 knots.

Sunday 21
Easing SSW groundswell. Sets to 3 – 4ft exposed breaks early, easing towards 2 – 3ft during the afternoon. Grading smaller elsewhere with size depending on exposure. WIND: Light and variable tending ESE 5 to 10 knots.

Monday 22
Leftover SSW swell. Around 1 – 3ft exposed breaks, inconsistent in the upper range. Grading smaller elsewhere depending on exposure. WIND: Early light and variable tending ESE 5 to 10 knots.

Overview
A fairly subdued southern Indian Ocean storm-track offers up a consistent run of small to mid-sized SSW swell across the archipelago this week, with a series of new SW swells set to follow into the final week of August. Over the course of the previous week we’ve seen a broad area of high pressure anchored over the central Indian Ocean keeping a lid on swell-potential for Indonesia; keeping storm activity confined to polar latitudes. Never the less, the polar storm-track was highly active over this time frame; characterised by a multiple frontal progressions embedded within a broad low pressure gyre spanning most of the southern Indian Ocean. A series of zonal (westerly) fetches supported by this activity supplies the archipelago with a constant run of small to mid-sized SSW groundswell through the remainder of the working week.

This commences with an initial drop in size by Wednesday; still running at 3 to 4ft across exposed breaks and levelling off around this size into Thursday. From there we should see a further drop in size into the 2 to 3ft range by Friday preceding the arrival of a new SSW swell this weekend. This low-period pulse is derived from a broad frontal progression currently tracking eastward, deep below Sumatera. As the front closes in on South-western Australia over the next 24 hours it aims a broad, 30 knot SSW fetch directly at Indonesia; remaining in effect inside our swell window until the low passes below the Australian mainland on Wednesday evening. The relatively close range of this source to Indonesia sends up a solid, mid sized pulse; probably peaking in the 4 to 5ft range across the more exposed breaks on Saturday before scaling down a foot or so by Sunday.

Latest deepwater virtual buoy readings for Bali reflect a slow decline in SSW groundswell through the remainder of the working week precedes a solid pulse of mid-period SSW on Saturday.

Latest deepwater virtual buoy readings for Bali reflect a slow decline in SSW groundswell through the remainder of the working week precedes a solid pulse of mid-period SSW on Saturday.

Long Range
This episode is projected to bottom out on Monday 22 at much lower 2ft levels across exposed breaks – with any luck marking a low-point in surf-heights preceding the arrival of a new round of SSW groundswell on Tuesday 23 August. This pulse has comparatively distant origins; spawned by a moderate-strength low pressure system currently situated deep below the Mozambique Channel. The storm supports a broad area of WSW gales below the 50S parallel – and it should continue to support this fetch as it migrates further eastward across southern Indian Ocean over the next couple of days. This modest fetch is only projected to support maximum seas and swell in the vicinity of 20 to 25ft, well below Madagascar – and it’s fair to say this doesn’t present any major swell potential for Indonesia; probably only generating a modest push in size into the 2 to 4ft range on Tuesday 23 and Wednesday 24 August.

The good news is latest computer modelling picks up a succession of stronger low pressure systems developing in the wake of this first low. This commences with a vigorous low sweeping up below South Africa and Madagascar on Thursday, generating significant wave heights of 30 feet. A subsequent pulse of SW groundswell emanating from this source is loosely projected to make landfall across Indonesia on Friday 26 and Saturday 27 August at stronger 3 to 4ft levels. This is closely followed by an even stronger, albeit very compact low pressure intensifying over the region this weekend; giving rise to a second, longer period pulse that’s likely to reinforce surf-heights during Sunday 28 and Monday 29 August. At this early stage there’s still some flexibility in projected arrival times and wave-height, so check back next week for clearer guidance on these episodes.

Beyond that we may see a lull in storm activity flowing through to a period of small to tiny SW swell prevailing throughout the archipelago into the opening days of September. This will also become clearer in next week’s update.

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